There is increasing evidence that nitric oxide (NO), a multipurpose messenger molecule generated from the amino acid L-arginine by nitric oxide synthase (NOS), plays a role in a variety of airway functions including vascular and airway smooth muscle tone, host defense, and pulmonary neurotransmission. In the present study, we investigated the role of NO in the regulation of airway epithelial ion tmsport function in vitro and transepithelial potential difference (PD) in vivo. Additoin of neurokinin A (NKA) and substance P (SP) increased short-circuit current of canine cultured tracheal epithelial cells in a concentratino-dependent manner, and these effects were abolished by dephenylamine carboxylate but not by amiloride. Tracheal transepithelial PD was also increased by NKA and SP.Preincubation of cells or tracheal perfusion with NG-nitro-L-arginine methylester (L-NAME,1 mM) attenuated the NKA- and SP-induced increase in short-circuit current and the amiloride-sensitive PD,causing a rig
… Morehtward displacement of the dose-response curves, whereas NG-nitro-D-arginine (D-NAME,1 mM) did not. The inhibitory effect of L-NAME was reversed by L-arginine (10 mM) but not by D-arginine (10 mM). The release of NO was determined by a real-time measurement of NO concentration ([NO]) in the perfusate using specific amperometric sensors for this molecule. NKA and SP increased [NO] in a dose-dependent manner. Therefore, tachykinins increase short-circuit current in vitro and amiloride-sensitive PD in vivo, which probably reflect Cl movement from the submucosa toward the respiratory lumen in tracheal mucosa and that NO generation by epithelial cells may be involved in this process.1)in vitroの系培養気道上皮細胞をUssing chamberにマウントし、voltage clampの条件下でshort-circuit current(Isc,短絡電流)を測定した。ニューロキニンA(NKA)およびサブスタンスP(SP)は濃度依存的にIscを増加させ、その効果はamilorideの影響を受けなかったが、diphenylamine carboxylateにより消失した。さらに、L-NAMEの前処理によりIsc反応性は著明に減弱し、L-arginineにより回復した。2)in vivoの系気管粘膜のtransepithelial potential difference(PD)は、SP、NKAにより増加し、その効果はIscと同様、L-NAMEにより選択的に抑制された。2.NO産生の評価ポーラログラフィーの手法を用い、NO産生を直接評価した結果、NKASPは、培養気道上皮細胞および気管粘膜表面からのNO遊離を増加させた。3.NOSサブタイプの決定モノクローナル抗体を用いた検討では、上皮細胞に存在するNOSはcNOSであった。以上の一連の実験成績より、タオキニンは気道上皮細胞のcNOS由来のNO産生を介し、Clイオン分泌を亢進させることが明らかとなった。 Less